OAKLAND — Still unconvinced about a multibillion dollar plan to keep the Raiders in Oakland, the NFL’s stadium czar was in the East Bay Wednesday pressing team executives and local officials for signs of progress.

The visit from NFL Executive Vice President Eric Grubman, who is overseeing the league’s anticipated return to Los Angeles, comes as Oakland and Alameda County have begun working in tandem with a private developer to keep the football team from moving south once again.

Grubman, who scolded city leaders for their inaction during his last East Bay visit several months ago, continued to apply pressure earlier this week during a visit to San Diego, which is fighting to keep its team.

Speaking on 1090-AM in San Diego, Grubman said that of the three cities at risk of losing their teams to Los Angeles, only St. Louis had produced a clear financing plan for a new stadium.

In perhaps a bigger blow to Oakland’s effort to keep the Raiders, Grubman told members of San Diego’s stadium committee that the NFL did not want stadium financing to be dependent upon additional development surrounding the facility “because it will take far too long to get it done, and bringing in a developer would just mean another mouth to feed,” according to UT San Diego.

Pairing a privately-financed $1 billion stadium with thousands of new homes, a hotel, shopping center and office complex is at the heart of Coliseum City — Oakland’s ambitious and often-criticized proposal for keeping the Raiders.

The NFL’s aversion to tying stadium development to ancillary projects stems from its desire for the team to have ultimate control over any stadium development, said Robert Boland, a professor of sports economics at New York University.

However, Boland said the NFL’s concerns over Coliseum City could dissipate if Raiders owner Mark Davis fully embraces it. “If Mark Davis and the Raiders are happy in Oakland, the NFL will be happy,” he said. Davis has said that he wants to stay in Oakland and is open to Coliseum City, but has not yet committed to the project.

Grubman was not available for comment Wednesday after attending the meeting at Raiders headquarters in Alameda.

Alameda County Supervisor Scott Haggerty called the meeting productive, but said Grubman still needed convincing that progress was being made.

“He is going to continue to light a fire under us,” Haggerty said. “The city and county are working together to move this along quickly. We understand the timeline.”

The Raiders, San Diego Chargers and St. Louis Rams are all in play for moving to the Los Angeles area in temporary facilities as early as next year. The Raiders and Chargers are working on a stadium plan in the city of Carson, while continuing to seek a new facility in their home markets. The Rams are further ahead on a proposed football stadium in Inglewood.

Since the Raiders announced their interest in Carson, Oakland and Alameda County have begun discussions with their development partner, San Diego businessman Floyd Kephart, to advance Coliseum City, which would be built on the 120-acre Coliseum complex in East Oakland that they jointly own.

Numerous hurdles remain, however, including lining up private investors and figuring out how to publicly fund needed infrastructure improvements at the site that could top $100 million.

Haggerty said that Kephart, who was also at Wednesday’s meeting, was working on putting together the framework of a deal within the next few weeks that could potentially work for both the Raiders and taxpayers. Kephart is required to show progress on several fronts by June 21.

Haggerty said he has tried to quell the league’s concerns about Coliseum City being about far more than a new stadium for the Raiders.

“I think this is more than just an excellent opportunity for the NFL to be involved in the revitalization of a stadium,” he said. “It an opportunity for the NFL to help change the face of an entire city.”